Synergistic insecticidal compositions



United 2,960,430 SYNERGISTIC 'INSECTICIDAL COMPOSITIONS Garman, Baltimore, Md.,

No Drawing. Original application Mar. 24,

No. 496,596. Divided and 1958, Ser. No. 767,284

5 Claims. (Cl. 167-22) 1955, Ser. this application Oct. 15,

This-invention relates broadly to insecticidal compositions, and more particularly to insecticidal compositions containing phenyl N-methylcarbamate and 0,0-dimethyl S-(1,2-dicarbethoxyethyl) dithiophosphate, hereinafter referred to as Malathion. More particularly, this invention relates to synergistic insecticidal compositions of these compounds wherein the insecticidal effectiveness of each component is enhanced by the presence of the other to produce an unexpected combined effect.

When two or more substances in combination show an unexpectedly high activity, as, for instance, insecticidal activity, the resulting phenomenon is called synergism. The mechanism of synergism is by no means understood. It is, in fact, quite probable that it differs with different synergistic combinations. The term synergism can be defined, however, as a cooperative action which is encountered in combinations of two or more biologically active components in which the combined activity of the two components exceeds the sum of the activities of the components when used alone. The insecticidal activity of the mixed components cannot be predicted from known values of the individual components, but is unpredictable and depends on the individual activity of neither.

It is an object of this invention to provide insecticidal compositions of enhanced killing power. Another object of this invention is to produce novel compositions containing compounds capable of synergizing the knockdown and killing properties of individual toxicants. A further object of this invention is to provide compositions including a relatively toxic phosphorus containing insecticide in which superior insecticidal activity is obtained because of the synergistic effects, but in which the ultimate toxicity to warm-blooded animals is greatly reduced because of the lower concentrations of the phosphorous compounds required when used in combination with the relatively less toxic carbamates. Other objects and advantages of the invention will become apparent from the description of the invention set forth below.

According to this invention, there are provided synergistic insecticidal compositions comprising 0,0-dimethyl S-(1,2-dicarbeth0xyethyl) dithiophosphate, hereinafter called Malathion, and phenyl N-methylcarbamate. This carbamate may be prepared as described in copending application Ser. No. 812,113, filed May 11, 1959.

The synergistic insecticidal compositions of this invention may be used on a wide variety of insect and mite species, but are particularly eflective against such insects as the two-spotted spider mite, harlequin bug and Mexican bean beetle. The combinationsare highly effective and economical to use for such large-scale insecticidal requirements as the control of truck crop, forage crop and orchard insects.

The synergistic compositions of this invention can be formulated as aqueous emulsions, as dry or wettable powders, as solutions or in any other suitable vehicle. The insecticidal compositions can be utilized as sprays, as dusts, as Aerosol mixtures, insecticidal coating comatent O positions, and as residues. In general, they can be applied by methods commonly used for control or eradication of insects, mites and the like. Thus these insecticidal compositions can be formulated with solvents, diluents and carrier media, adhesives, spreading, wetting and emulsifying agents and other ingredients.

The relative proportions of the active ingredients as well as inert carriers, solvents, dispersants and the like may vary within wide limits.

Thus the relative proportion (ratio) of the Malathion to the carbamate ester can range from 20 parts of the former per 1 part of the latter to 1 part of the former per 40 parts of the latter and preferably about 1 part of the former to about 10 parts of the latter.

The quantities of the component toxicants in the final insecticidal compositions can range from 0.01% to 25.00% for the Malathion and from 0.05% to 50.00% for the carb-amate, and preferably from 0.10% to 10.00% for the Malathion andfrom 0.10% to 25.00% for the carbamate.

The procedures of the testing methods are described below. The details of the test experiments including the type of formulation and mode of application or dosing, and the species of insects which served as test subjects are given in the examples.

Insects used vin the testing included the house fly (Musca domesticzz L.), Mexican bean beetle (Epilachna varivestis Muls.), pea aphid (Macrosiphum pisi. [Kltb.] two-spotted spider mite (T etranychus bimaculatu's Harvey), harlequin bug (Murgantia histrion'ica [Hah1]) and squash bug (Anasa tristis).

The test methods used are described as follows:

DUST TOWER METHOD This general method is described in the following reference, Moore, J. Econ. But. 43, No. 2, 188-190 (1950).

The dusting apparatus consists of a vertical glass cylinder, 34 inches high and 8.5 inches in diameter, into which the appropriate dust sample is discharged through a small hole in the center of the cover, by means of a small laboratory duster operating at an .air pressure of 40v p.s.i.g. The duster assembly comprises a 10 ml. beaker, into which the weighed sample is placed, and fitted with a rubber stopper through which pass the air inlet and dust outlet tubes, both of which are made of inch diameter copper tubing. At the outer end of the air inlet tube is .a trigger valve that serves as a control for dispensing the dust. The inner .end of this tube reaches nearly to the bottom of the beaker. of it is sealed but, along the sides, seven 0.032 inch holes are drilled at irregular intervals which serve as air inlets. Such an arrangement causes pronounced turbulence of the dust and thus insures exhausting the complete sample from the beaker. from the top of the tower.

After discharge of the sample into the tower, there is allowed a 2-minute settling time before removal of foliage or insects being treated. A Weighed metal plate is placed in the tower each time a test is made, and by weighing the amount of dustdeposited on it, it is then possible to calculate the amount applied per acre.

Because of day-to-day variations in the results obtained by this test method, comparisons among the individual components and their combinations were made simultaneously in order to minimize this source of variation.

Slight modifications in this test employed for specific insect species are as noted below.

Mexican bean beetle.ln tests usingthis insect, bean foliage was dusted then infested with fourth instar Mexican bean beetle-larvae. These were allowed to feed for The, dust outlet tube forms an arch beaker to the top of the glass dusting The end 1 24 hours, then treated foliage was replaced with untreated. Mortality records were made at 48 hours.

T wo-spotted spider mite-In tests on two-spotted mites, the mites were confined to the upper surfaces of potted bean plants by a Tanglefoot ring. The bean plants were placed in the glass tower and the mites directdusted. Mortality readings were taken in 24 hours. Only adult mites were used in determining mortality counts.

Pea aphid-Pea plants were infested with pea aphids and direct-dusted. Mortality readings were taken at 24 hours.

Harlequin bug.-The foliage was dusted, then infested with harlequin bugs. Mortality counts were taken in 24 hours.

Squash bug-For this test squash leaves were collected in the field and the cut ends of the stern were wrapped in moist cotton. Individual leaves were then placed in 3.5 inch Petri dishes and dusted as described above. Each treated leaf was then infested with last instar squash bug nymphs and the covers of the Petri dishes were replaced. At the end of 24 hours the treated leaves were removed and frresh untreated leaves were introduced into the dishes. Mortality counts were taken after the 4 Serial No. 496,596, filed March 24, 1955, now abandoned, which is a continuation-in-part of Serial No. 427,374, filed May 3, 1954, now abandoned.

We claim:

1. Synergistic insecticidal compositions comprising 0,0- dimethyl S-(l,2 dicarbethoxyethyl)dithiophosphate and phenyl N-rnethyl carbamate, wherein said components are employed in a ratio of from about 10 parts of said carbamate ester per part of said dithiophosphate to about 1 part of said carbamate ester to about 5 parts of said dithiophosphate.

2. A method of killing insects which comprises applying to the insects and their habitat a synergistic insecticidal composition comprising 0,0-dimethyl S-(1,2 dicarbethoxyethyl) dithiophosphate and phenyl N-methyl carbamate, wherein said components are employed in a ratio of from about 10 parts of said car-bamate ester per part of said dithiophosphate to about 1 part of said carbamate ester to about 5 parts of said dithiophosphate.

3. A composition according to claim 1 wherein said components are employed in the ratio of about 10 parts of said carbamate ester to about 1 part of said dithiophosphate.

4. A composition according to claim 1 wherein said bugs had been on the untreated leav for 24 hours, 25 components are employed in the ratio of about 5 parts of Table 1 Carbamate Phosphate Rate Test Method Test Subject Mortality Dust Dust (lbs/A.) (Percent) R Gone. Name Cone.

(Percent) (Percent) Methyl 1 Dust Tower-.." 2 Malathionu 0.25 39 D0 1 d0 0.25 94 10 .dc Mexican Bean Beetle 1 Mal-athion" o 3 do do 73 This table demonstrates the effectiveness of the synergistic combinations of this invention on a variety of insects.

said carbarnate ester to about 1 part of said dithiophosphate.

5. A composition according to claim 1 wherein said Table 2 Oarbamate Phosphate Rate Mortality Dust Dust (lbs/A.) Test Method Test Subject (Percent) Name Cone Name Cone.

(Per- (Percent) cent) Phenyl N-Methylcarbemate. 0. 1 10. 2 Dust Tower.-. Mexican Bean Beetle--. 0 D 0.1 22. 2 do g The results of the tests summarized in Table 2 demonstrate the marked synergism of the insecticidal compositions of this invention using wide ratios of active ingredients.

This application is a division of copending application components are employed in the ratio of from about 2 parts of said carbamate ester to about 1 part of said dithiophosphate.

(References on following page) 2,503,390 Jelinek Apr. 11, 1950 OTHER REFERENCES Gysin May 25, 1954 5 Chem. Age., vol. 63, No. 1631 (1950), p. 540.

Sharp: Agr. News Letter, January-February 1952, pp. 1-3.

Roark: U.S. Dept. Agr. Bulletin E-344 (May 1935), pp. 2-6.

Frear: Chem. of the pesticides, 3rd ed., January 1955, pp. 73-91. 

2. A METHOD OF KILLING INSECTS WHICH COMPRISES APPLYING TO THE INSECTS AND THEIR HABITAT A SYNERGISTIC INSECTICIDAL COMPOSITION COMPRISING O,O-DIMETHYL S-(1,2 DICARBETHOXY-ETHYL) DITHIOPHOSPHATE AND PHENYL N-METHYL CARBAMATE, WHEREIN SAID COMPONENTS ARE EMPLOYED IN A RATIO OF FROM ABOUT 10 PARTS OF SAID CARBAMATE ESTER PER PART OF SAID DITHIOPHOSPHATE TO ABOUT 1 PART OF SAID CARBAMATE ESTER TO ABOUT 5 PARTS OF SAID DITHIOPHOSPHATE. 